1. Field of the Invention
The present invention relates to a gas-liquid separating apparatus applicable to an electric power plant or the like.
2. Description of the Prior Art
One example of a gas-liquid separating apparatus in the prior art is shown in FIGS. 10 to 13.
This apparatus includes a separator 12 disposed within a drum 1 as shown in FIG. 10. The right half of FIG. 10 shows the outer appearance of the separator 12, while the left half shows the separator 12 in section. Furthermore, a mist separator 5, a rectifier plate 6 for preventing vortexes, and the like are provided within the drum 1.
As shown mainly in FIGS. 11 and 12, the separator 12 includes a cylinder 9, a cap 18 and a secondary separator 11. This secondary separator 11 consists of a stack of corrugated plates or of a structure having the profile of a fan blade.
Now, the flow of gas-liquid mixture in the apparatus will be described. In FIG. 10, a gas-liquid mixture 19 fed from a boiler evaporator tube enters a separator inlet 15 through inlet piping 2. The gas component of this gas-liquid mixture is steam, and the liquid component is water. The gas-liquid mixture 19 fed through the separator inlet 15 enters the cylinder 9 in a direction tangential to the cylinder 9 as shown in FIG. 13, and thus flows, as designated by reference numeral 8, along the inner wall surface of the cylinder 9, whereby centrifugal separation of the gas and liquid is effected. The separated steam is discharged from the secondary separator 11 through a cap 18 to a gas-phase section of the drum 1 as designated by reference numeral 28 in FIG. 10. Also, the separated liquid flows out from a primary isolated water outlet 17 to a liquid-phase section of the drum 1 as primary isolated water 20.
It is to be noted that because the centrifugal separation in the cylinder 9 is not sufficient, as shown in FIG. 11, liquid 7 also flows into the secondary separator 11. As shown in FIG. 10, the liquid 7 flows through a gap 16 and out the bottom 10 of the cap 18 as secondary isolated water 13. This water 13 drips onto a gas-liquid boundary surface 14 within the drum. Likewise, steam is also entrained in the primary isolated water 20 flowing from the primary isolated water outlet 17 into the liquid-phase section of the drum. The steam in the gas-phase section of the drum 1 is fed from a mist-separator 5 through steam outlet piping 3 to, for instance, a turbine. The liquid in the liquid-phase section is rectified by a rectifier plate 6 to prevent the formation of vortices, and thereafter it is returned to, for instance, an inlet of the boiler evaporator tube through a down comer 4.
In the prior art, the primary isolated water 20 flowing from the primary isolated water outlet 17 and containing steam, enters the liquid-phase section of the drum 1 as shown in FIG. 10 while retaining a velocity in a rotary direction associated with the flow 8. Due to this velocity and the force of gravity, the primary isolated water 20 flowing out from the primary isolated water outlet 17 swirls in the same direction as the flow 8. Due to this flow, strong and fast in-drum liquid flows 22 are directed from the primary isolated water outlet 17 towards the down comer 4. Hence, the primary isolated water 20 flowing out from the primary isolated water outlet 17 is drawn into the in-drum liquid flow 22 in a short period of time, and flows through the down comer 4.
Therefore, the prior art gas-liquid separating apparatus has a disadvantage in that the time available for gas-liquid gravitational separation of the primary isolated water 20 containing steam in the liquid phase section of the drum 1 is not sufficient. Hence it was difficult to achieve gas-liquid separation with high efficiency.
In addition, a gas column is formed at a central portion of the cylinder 9 as a result of the swirling flow 8. Depending upon the flow rate of the gas-liquid mixture 19, sometimes the bottom of the gas column would reach below the primary isolated water outlet 17, and a large amount of steam would directly flow into the liquid-phase section of the drum 1. Therefore, the prior art gas-liquid separating apparatus also has a disadvantage in that highly efficient gas-liquid separation could be achieved only over a small range of flow rates.